Drug injecting youth and young adults are disproportionately affected by HIV disease. Injection drug use is inextricably connected with the social context in which it occurs. Thus, it is critical to understand this problem within the greater social system in which it exists, to conceive of the multiple levels of the social environment through which influences can be exerted, and to disaggregate and then identify how these influences regulate drug injecting behavior. This training fellowship will support the preparation, and implementation of a secondary data analysis of existing data collected via a cross-sectional study undertaken to understand the HIV risk and protective behaviors of young women and peers, ages 15 to 23, who are either injection drug users (IDUs) and/or sexual partners of IDU. A multilevel analysis approach will be used to model regulatory social contextual influences, at the individual and social network levels, on HIV risk behaviors related to injection drug use. Conceptualization of multiple levels of influence regulating HIV risk behaviors and the reciprocality between levels is a novel approach to research in the areas of social networks, injection drug use, and HIV. This work also has relevance for informing individual and social network-level HIV prevention interventions for high risk youth.